In constructing a building such as a house, it is common that openings for receiving doors and windows are first roughly framed in with wall studs, which usually are made of wood. Subsequently, the rough framed openings are finished with a wooden door or window jamb assembly, which often is provided with a decorative brickmold that abuts the brick or siding on the outside of the building. In some instances, the brickmold is milled as an integral part of the jamb frame members and in other instances the brickmold is nailed or stapled to the jamb members along their outside edges. In door jamb assemblies in particular, a peripheral lip or stop usually is milled into the wooden support members of the jamb and the stop extends around the inner periphery of the jamb. In use, a closed door mounted to the jamb assembly rests against the stop. In many instances, the stop bears a weather strip that seals against the closed door to prevent drafts.
In sidelight door jamb assemblies, a pair of spaced vertical mullions extend between the sill and the header of the assembly to form a central opening for receiving a hinged door and a pair of narrow side openings on either side of the door for receiving sidelight windows. Such mullions typically are formed of a pair of back-to-back wooden supports that have been milled along their exposed faces to provide stops for abutting a closed door or receiving and securing the sidelight windows. A strip of decorative molding is commonly nailed along the outside edges of the mullion supports to cover their outside edges, to cover the junction between the supports, and to lend a pleasing appearance to the jamb assembly.
A traditional method of fabricating a door jamb assembly is to mill the peripheral support members of the assembly from larger pieces of a high quality clear wood. In this process, a relatively wide thick piece of wood for each leg of the assembly is passed through a milling machine and unwanted portions are cut or milled away and discarded as sawdust. The milling process produces the raised inside peripheral stops and other structural features of the support members. Obviously, this process is wasteful and is becoming more and more expensive in light of the ever-increasing cost of lumber. In some instances, the entire cross-section of each frame member, including the brickmold, is milled as a unitary piece from a wide thick piece of lumber. In other instances, the frame members are milled from two pieces of wood that fit together to define the finished jamb shape. The inner peripheral supports may be milled from relatively thinner pieces of wood to define the frame and door stop and the brickmold may be nailed along the outer edges of the supports to define the finished shape of the jamb. In either case, significant amounts of expensive lumber are required as is time consuming, expensive, and wasteful machining steps. All of this adds to the final cost of traditional door jamb assemblies. Further, and perhaps even more pertinent, is the fact that the exposed wooden brickmold and the molding along the mullions of side light door jamb assemblies requires periodic painting and maintenance in order to prevent rotting as a result of exposure to the weather. Even with the most careful maintenance, these exposed wooden portions of door jamb assemblies can, over time, begin to rot from within whereupon the entire door jamb assembly usually must be replaced. Rot due to moisture can be a particular problem at the bottom ends of the vertical jamb members where they meet and are secured to a door sill assembly. Rain water that runs down onto the door sill assembly tends to be wicked into the bottoms of the vertical jambs causing subsequent rot of the wooden material of the jambs.
Door and window jamb assemblies have been developed that are wholly or partially comprised of extruded thermoplastic portions. For example, U.S. Pat. No. 4,430,830 to Sailor teaches a jamb for mounting a window or door in an opening of an existing structure. The jamb includes an extruded plastic or metal outer frame comprising the stop, a wooden inner frame or jamb for support of the extruded outer frame, fasteners for attaching the outer frame at the window or door opening, and a molded cover that secures the outer frame and conceals the fasteners attaching the frame to the structure. In Sailor, the portion of the plastic outer frame forming the stop and brickmold are hollow and thus may not provide sufficient strength to the frame. The hollow nature of the brickmold makes it unsuitable for receiving standard nails that hold the assembly to the frame. Non-carpentry standard fastening means are thus employed, which is distasteful to many carpenters. In addition, this jamb assembly requires the use of an auxiliary cover to conceal the fasteners attaching the frame to the building structure.
U.S. Pat. No. 5,058,323 to Gerritsen teaches a jamb cladding and brickmold assembly that provides a plastic member that either wraps around a wooden jamb with a milled stop or that wraps around a wooden jamb and provides its own plastic stop. An attachable brickmold is also included. This assembly, like that taught by Sailor, has hollow portions unsuitable for holding nails and liable to be punctured or otherwise deformed by heavy use or forcible contact. U.S. Pat. No. 5,182,880 to Berge, Jr., et al., teaches a cladding and brickmold apparatus similar to that taught by Gerritsen in that it wraps around a combination wooden jamb and stop. Thus, this device requires the use of a wooden jamb with stop and requires that the wood be milled to form the stop. The prior art does not teach a unitary stop and brickmold assembly made of substantially solid extruded thermoplastic material.
U.S. Pat. No. 5,661,943 of Hagel discloses a milled wooden door frame assembly wherein the bottom sections of the vertical jambs are formed from a composite material made of wood particulate that is mixed with resins. These bottom sections are milled or otherwise formed to have the same profile as the wooden portions of the vertical jambs and are joined to the wooden portions with finger joints. The goal of this jamb structure is to address the problem of rot and decay at the bottoms of the vertical jambs where the jambs meet the door sill. While the Hagel frame is an improvement over traditional all wooden door frames, it nevertheless has its own inherent problems and shortcomings. For example, The finger joint that joins the composite bottom sections of the vertical jambs to the upper portions of the jambs tends to be relatively weak, and can be broken off, especially prior to the attachment of brickmold after installation of the frame. In addition, the vertical jambs and head jamb must still be milled to define the finished profile of the frame after the composite bottom portions of the vertical jambs are joined. Obviously, this is an expensive, wasteful, and time consuming task.